There are many types of grinding machines. They mostly rotate in a unidirectional manner at low speed and high torque to process rough surfaces. To suit different grinding surfaces, they can be classified in flat grinding and side grinding by the operation mode. As the grinding machines are designed in many different types, they are widely used in many industries such as iron work, machinery, wood working, molding, automobiles and motorcycles, repairs and maintenance, glass fibers, electronics, and the like. Different sizes of granule of the grinding piece may be selected to perform required operations such as polishing, rust removing, glue removing, grinding, wax polishing, edge trimming, drilling, or the like.
Refer to FIG. 1 for a typical operation section of the conventional unidirectional rotation grinding machine that rotates at low speed and high torque. It includes a fastening mechanism. As shown in the drawing, the operation section has an output shaft 6 extending outwards. The output shaft 6 is coupled with a bearing 7 and screws a coupling head 1. The coupling head 1 has a fastening hole 11 and is engaged with a fastener 2. When in use, a grinding piece 4 is sandwiched and anchored between the coupling head 1 and the fastener 2. The output shaft 6 is driven by a driving mechanism to rotate at high speed to drive the grinding piece 4 to rotate in one direction. When the unidirectional grinding machine performs grinding operation, sparks, grinding debris, powders or dusts are inevitably generated. The sparks may spew to the surrounding and cause fire when inflammable goods are around. Dusts produce environmental pollution. The grinding debris scatter around and may cause severe hazards to the health and safety of operators.
Moreover, due to the conventional grinding machines rotate in one direction, when grinding a narrower working piece or corners, the grasp section of the grinding machines is constrained due to design limitation and allows only surface machining to be performed on the working piece. Some corners cannot be machined smoothly by the conventional grinding machines, and operators have to adopt other operating gestures or approaches to do machining operation. Those abnormal operation methods often affect grinding quality and produce defects on the machining surface.
In addition, when the grinding piece 4 rotates at high speed, a greater torque occurs on the exposed section of the output shaft 6. Because of the length of the output shaft 6 or uneven distribution of the torque, the output shaft tends to occur deformation or even damage.